The present invention relates to construction of three-dimensional objects from multiple layers of sheet material and, in particular, it concerns a method for facilitating the removal of residues from adjacent to such objects.
It is known to build-up three-dimensional structures by attaching together layers of sheet material each cut to the contour of a thin slice of the object. This technique can be used in a wide range of applications, and has particular advantages for rapid construction of small numbers of individual prototypes and models using CAD (computer-aided-design) techniques, or to facilitate the manufacture of three-dimensional objects using CAM (computer-aided-manufacture) techniques. An example of this technique is described in U.S. Pat. No. 3,932,923 to DiMatteo. In most implementations of this technique, the individual layers are first contoured, and then the contoured layers are stacked and bonded together to form the three-dimensional object. This tends to lead to low precision due to registration problems in alignment of the pre-contoured layers.
U.S. Pat. No. 5,071,503 to Berman proposes an alternative approach in which each layer is bonded to the partially-built three-dimensional object by selective application of adhesive and only then is contoured to the required shape. Contouring after bonding of the layer increases the precision by avoiding registration problems. PCT Patent Publication No. WO99/34976 proposes a technique for forming three-dimensional structures of this type employing sheets of polymer materials coated on one side with adhesive, such as are commonly used for laminating applications and the like. Selective adhesion of the layers is achieved by applying a releasing agent to prevent adhesion in regions lying outside the contour of the object to be formed.
While the construction of three-dimensional objects is achieved very effectively by selective adhesion and cutting to shape of sheet material, the removal of the unwanted residues around the object can be problematic. If the residues were to be adhered to each other, large blocks would be formed which, depending upon the shape of the object, would be very difficult or impossible to remove. To avoid such problems, commercial devices based on this technology typically perform selective adhesion so that the layers are attached exclusively within the contours of the object. As a result, the object is typically surrounded and/or filled with very numerous separate sheets of residue material which must then be removed manually. This can be a very laborious and time-consuming job.
An alternative approach is proposed by U.S. Pat. No. 5,637,175 to Feygin et al. in which the residue regions are attached to the adjacent sheets but are cut in a cross-hatched fashion to weaken them. This is said to result in a matrix structure which is attached to the object but relatively weak in strength, so that it can be removed by mechanical means. This clearly adds an additional non-trivial production step.
There is therefore a need for a method for facilitating the removal of residues from adjacent to a three-dimensional object formed from attachment of multiple layers of a sheet material.